1. Field of Invention
This invention is for sampling chemical and biological parameters in ground-water wells, specifically the apparatus collects a time-averaged or composite sample and makes possible real-time analyses.
2. Discussion of Prior Art A search of the literature has indicated that no invention exists for sampling ground water which combines a pumping apparatus, sorption unit and packer. A literature search has shown an invention which combines a pumping apparatus with a sorption unit (Manual of Ground-Water Quality Sampling Procedures, U.S. Environmental Protection Agency, Ada, Okla. 1981). This invention positions the pumping apparatus at the bottom of the well casing and the sorption columns at the surface. This configuration requires a powerful pump to lift the water to the surface and a tube connecting the pump with the sorption columns. The apparatus does not address some of the problems which my invention was designed to correct. The main differences are: (1) the earlier invention does not include a packer which is used to isolate the ground water from the atmosphere, (2) the earlier invention requires the sorption tube to be located above the pumping apparatus which introduces errors in sampling trace organics and metals because of pressure and temperature differentials, sorption of the sample on the connecting tube and other losses which can occur when the sample is altered during the sampling process. Additionally, the configuration of the earlier sampler is not amenable to remote sampling locations because of the power and security problems.
A tube and cartridge method was used in a ground-water investigation by Pankow et al. (Ground Water, Vol.23, No.6, November-December 1985). The sampler consisted of a sorption colomn, a flow restrictor, and a tube leading to the ground surface. The device was lowered down a well, and the water-column pressure forced the sample through the cartridge. The apparatus lacked both a pumping unit and a packer. However, the end of the sampling tube was introduced directly into the ground water. This eliminated many of the problems which could have caused error in the previous sampler. This sampler was limited in its ability to obtain a time-averaged sample because of the lack of a programmable pumping unit and packer.